Exploring the relationships between genetic, linguistic and geographic distances in Bantu-speaking populations

Objectives:The predominance of Bantu languages in sub-Saharan Africa has sparkeda large debate over the processes through which they came to disperse over timeand space—the“Bantu expansion.”The overall genetic similarity shown by Bantu-speaking populations indicates that movement of people occurred too, but the extentof the correlation between genetics, linguistics and geography has been a matter ofdebate among scholars of different disciplines. In this work, we aim to investigatehow genetic, linguistic and geographic distances relate to each other in Bantu-speaking populations.Methods:We analyzed genome-wide SNP array data from a set of 37 Bantu andnon-Bantu-speaking populations together with related linguistic and geographic data.Due to the complex demographic relationships resulting from events of admixture inthe history of these populations, we develop and implement a method for controllingthe signatures of admixture.Results:Genetic distances were only minimally correlated with linguistic and geo-graphic distances, possibly as the result of gene flow from neighboring groups intoBantu-speaking populations. When signatures of admixture are controlled for, thecorrelation of genetic data with linguistic and geographic distances significantlyincreases.Discussion:The increase of the correlation between linguistic and genetic distancesafter the signatures of admixture are taken into account is in agreement with a sce-nario of spatial co-dispersal of languages and people. Additional specific cultural anddemographic dynamics have probably further affected the relationship between lan-guage and genetics, which will be necessary to take into account when integratingmultidisciplinary data to reconstruct the history of populations.